Slashdot videos: Now with more Slashdot!

View

Discuss

Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).

hypnosec writes "CERN has revealed that the Large Hadron Collider (LHC) is going into hibernation and will be shut down for a period of two years for upgrades. The LHC will go through a maintenance and upgrade phase starting in March that will bring the atom smasher up to speed with its maximum energy levels. From the article: 'The machine that last year helped scientists snare the elusive Higgs boson – or a convincing subatomic impostor – faces a two-year shutdown while engineers perform repairs that are needed for the collider to ramp up to its maximum energy in 2015 and beyond. The work will beef up electrical connections in the machine that were identified as weak spots after an incident four years ago that knocked the collider out for more than a year.'"

Not far off - but the LHC power consumption is only ~0.3 GW and won't change much with the higher energy since the magnets are superconducting and most of the power goes into keeping them cold. However with a 27km circumference don't expect to find it mounted in the back of a Delorean anytime soon.

With the resolution of the NHL strike, a lot of Zambonis and their skilled operators will be shipped over to North America and thus won't be available for the regular icedowns required by the LHC track.

Hmm... Just when they get a whiff of the Higgs they shut down. Curious. Either "those in the know" have to have some time to make sure things like the LHC don't really find it, or they need a little time to reengineer the Higgs so as to make it less detectable.

I don't really know whether it will be or any use to reply to this post, but I will take my chance anyhow.

In extremely few words, shutting down the LHC has nothing to do with finding the Higgs Boson, as of now. The data from the particle collisions is NOT processed in real time. The data is stored and processed at a much slower rate compared to that of which it is produced. Already there's TONS of data that needs to be processed and analysed. The necessary data for determining whether there truly is a Higgs Boson or not is already there, waiting only to be looked at and analysed. The fact our ability to process $DATA is slower than our ability to produce $DATA has nothing to do with 'those in the know redesigning Higgs to fit their needs'.

Correct.
The shutdown was originally planned to start a month or so ago, but the run got extended to make sure we had the maximum number of collisions to sudy the Higgs boson in detail. It could not be extended more, because of issues with contracts planned long ago for this shutdown.
The LHC performed very well this year, but not above its own expectations, and therefore we have now a dataset which is big enough to say a few words about how this boson really looks like the Higgs boson, but to really characterize it further we need more data. For instance, with the data still being analysed, we know that the spin will not be unambiguously determined - well, depends on the definition; at least not with the usual 5 sigma.

The necessary data for determining whether there truly is a Higgs Boson or not is already there

Actually that is not quite correct. To really determine whether we have a Standard Model Higgs boson we need to see its decays into things called fermions (particles that make up matter) and so far we have only see it decay into bosons (particles that create forces). The problem is that the heaviest fermions the "Higgs" can create, b-quarks, are also created by different physics that is ~a billion times more likely than a Higgs decay so it's like try to find a piece of straw in a haystack (a needle is easy if you have a big enough magnet!). The next heaviest fermions, tau leptons - a very heavy cousin of the electron - decay in a way which makes them look very much like quarks and so, to a large degree, suffer the same problem (identifying taus in the trigger is something I actually work on).

So to be able to see these decays we need a lot of data and it is not entirely clear whether we will have enough in the current dataset to see these decays - my best guess is that we might hit 3 sigma "evidence" but without some very clever analysis I think a 5 sigma "discovery" is unlikely. In addition we also need to measure the spin of the Higgs to confirm that it is a scalar, spin-0, particle. This again requires large statistics and again I don't know that we have enough data yet - time will tell.

The big reason for the shutdown is for the energy upgrade. If this new particle really is the Higgs then we can expect new physics out there to explain why the Higgs is so much lighter than the planck scale - the energy where gravity becomes important (the reasons behind this are complex!). This new physics may also explain what Dark Matter is so there is a great deal of hope that getting the energy up to ~13TeV (which is what is expected after the upgrade) may give us access to this new physics.

Not curious at all. And, as mentioned in previous posts, the shutdown has been planned for several years already. If the Higgs' energy was higher than the roughly 125 GeV it seems to have, LHC would have found it a lot sooner.

The reason for not shutting down earlier was that they wanted to be sure that if it wasn't found by the time they shut down, then the accumulated data would be sufficient to rule out the Higgs. They calculated that in order to do that, they had to run until the end of 2012.

For how many years needs something to be known before it is no longer a revelation? Seriously, this schedule has been in the plans for several years, it was also clear from even before the initial start that before going to design luminosity (i.e. beam intensity in layman's speak) and design energy a shutdown for refurbishment would be necessary. This is no surprise at all -- after all running the world's highest energy particle collider (the LHC at 7 TeV) would necessarily teach us something about running a machine at even higher energies (the LHC which will run at 13-14 TeV starting 2014) that we didn't know before.

From reading the reports, I gather 'something' was found that aligned nicely with Peter Higgs' predictions, so it's (more or less?) considered "Higgs boson found!", and he got credit accordingly. Subject to further research & discoveries of course - as usual in the scientific process.

I was kind of surprised the upgrade will cost "only" 40 million. That is less than 1/2 of 1% of the $9 BN program cost. In other words their expenditures must be down a lot this year during the upgrade.

The use of the word "revealed" seemed odd to me to - the shutdown isn't something new or unexpected. But, given the literacy and intelligence of science journalism these days, I'm just glad that they managed to write the article without once mentioning "God Particle."

I'm just glad that they managed to write the article without once mentioning "God Particle."

That phrase would have been far less offensive if the newspaper prudes hadn't censored it. I was "God damned particle, because it was so elusive it pissed the researchers off that they hadn't found it. When the term was published in the popular press, "damned" was censored out.

Well all they are doing to accelerating a few atoms. you should not need very much power to accelerate masses that small.

You might think so based on the miniscule resting mass of the particles, but remember that they are being accelerated very close to the speed of light, so they gather a staggering amount of kinetic energy (and/or additional mass, relativistically). The LHC particle beam is the closest thing to the death star's destruction ray that humans have created. Each of the collider's two counter-rotating sets of particle bunches carries 360,000,000 joules of energy - about as much as 300 sticks of dynamite, or a passenger train moving 90MPH. The stored energy in the pair of beams could melt a ton of copper instantly. All that, in a "flying rod of protons" about 0.3mm in diameter and moving 186,000 miles per second. The LHC uses a pair of huge graphite cylinders 22 feet long and 2 feet in diameter to dispose of the accelerated protons. Each beam dump is water cooled and surrounded by 750 tons of radiation shielding deep underground. But even that isn't quite good enough on its own. The particles beam is deflected into a circular pattern as it is directed into the graphite absorber so the energy is spread over a larger volume to avoid excessively damaging the graphite.

Each beam is really a loop of proton bunches, since they circulate indefinitely around the ring. There are 2808 bunches per beam maximum, and each bunch contains about 1.15x10^11 protons. The bunch length is something like 8cm, and the diameter actually varies a lot but runs about a fraction of a millimeter through most of the ring, and focuses down to about 16 microns (hair diameter) at the crossing point where the beams collide. The design minimum bunch spacing is 25ns (about 25 feet at the speed of light), but they have been running wider spacing than that I think. The bunches are not uniformly spaced, either, since there are large gaps to allow time for the beam dump and injection apparatus to activate without getting proton blasted during switching.

It's a very small number of collisions compared to the number of protons. One source says something like 20 collisions per crossing, which works out to about 600 million collisions per second. That may seem like a large number, but it's extremely small compared to the number of protons passing close to one another every second!

250 to 350 mW is equivalent to 2.5 to 3.5 billion 100 watt light bulbs.With a "b", as in 2,500,000,000 bulbs.

According to the DoE, the average US household uses 1 kW of electricity at any given time.250 mW usage would be equivalent to the same amount of power consumption as a quarter of a million US homes (250,000)

Put another way, if you or I were to use this amount of electricity at home it would cost $25,000 every hour. In a 30 day period, the electric bill would total 180 million dollars ($180,000,000)

They get their power from France (Mostly nuclear) and Switzerland (lots of Hydroelectric). When the LHC is running, it can take the same sort of power as the whole of Geneva. I am not sure how they procure their power, but given the mild winter, power has been a lot cheaper than expected unfortunately the decision to extend the run was made some months ago and they may already have locked in the price.

But perhaps they did. At the exact moment the Mayan clocks ran out, so did our power, I didn't come back on for several hours. Afterwards, everything was the same, or was it? Perhaps we are under *new* management?

The LHC beam tunnel is just barely big enough for the beam line and magnets. The layout is as tight as a submarine. Getting magnets in and out is a huge pain. The original intent was that it wasn't going to be necessary to do that very often. It didn't work out that way.

But after the last failure, they discovered that the electrical connections between the sections weren't as solid as they needed to be. The trouble four years ago happened because a weld wasn't good enough. A connection went non-superconducting and became resistive, and all the energy stored in the associated superconducting magnets was converted to heat. The area of the joint exploded and most of the liquid helium in the system converted to gas, blowing out a lot of cryogenic plumbing.

Because of the tight spaces, tasks which ought to be done in parallel have to be done sequentially. That increases downtime.

The unfinished US Superconducting Supercollider had tunnels big enough for railroad trains. (It was in Texas and a pork program; what would you expect?) CERN built cheaper, but they pay for it in downtime.

I'm not sure if space is the issue here. You can bike in the tunnel (useful, since it's looong). [and by the way, the beamline is contained in the magnets, so that saves space;-)]
Parallellizing means also more expert manpower for less work: I could imagine it's practically impossible to train 1000 expert welders to each repair one joint.
Note also that the LEP tunnel that is housing now the LHC was far from cheap...

Unfortunately the way projects are funded, there is strong pressure to minimize the initial cost, even if the total cost in the long run will be higher. "operating" costs can usually be taken into account, but most funding agencies are very reluctant to spend more money not for future non-approved upgrades.